libavcodec/xsubdec.c

   1 /*
   2  * XSUB subtitle decoder
   3  * Copyright (c) 2007 Reimar Döffinger
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21 #include "avcodec.h"
  22 #include "bitstream.h"
  23 #include "bytestream.h"
  24
  25 static av_cold int decode_init(AVCodecContext *avctx) {
  26     avctx->pix_fmt = PIX_FMT_PAL8;
  27     return 0;
  28 }
  29
  30 static const uint8_t tc_offsets[9] = { 0, 1, 3, 4, 6, 7, 9, 10, 11 };
  31 static const uint8_t tc_muls[9] = { 10, 6, 10, 6, 10, 6, 10, 10, 1 };
  32
  33 static uint64_t parse_timecode(const uint8_t *buf) {
  34     int i;
  35     int64_t ms = 0;
  36     if (buf[2] != ':' || buf[5] != ':' || buf[8] != '.')
  37         return AV_NOPTS_VALUE;
  38     for (i = 0; i < sizeof(tc_offsets); i++) {
  39         uint8_t c = buf[tc_offsets[i]] - '0';
  40         if (c > 9) return AV_NOPTS_VALUE;
  41         ms = (ms + c) * tc_muls[i];
  42     }
  43     return ms;
  44 }
  45
  46 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
  47                         const uint8_t *buf, int buf_size) {
  48     AVSubtitle *sub = data;
  49     const uint8_t *buf_end = buf + buf_size;
  50     uint8_t *bitmap;
  51     int w, h, x, y, rlelen, i;
  52     GetBitContext gb;
  53
  54     // check that at least header fits
  55     if (buf_size < 27 + 7 * 2 + 4 * 3) {
  56         av_log(avctx, AV_LOG_ERROR, "coded frame too small\n");
  57         return -1;
  58     }
  59
  60     // read start and end time
  61     if (buf[0] != '[' || buf[13] != '-' || buf[26] != ']') {
  62         av_log(avctx, AV_LOG_ERROR, "invalid time code\n");
  63         return -1;
  64     }
  65     sub->start_display_time = parse_timecode(buf +  1);
  66     sub->end_display_time   = parse_timecode(buf + 14);
  67     buf += 27;
  68
  69     // read header
  70     w = bytestream_get_le16(&buf);
  71     h = bytestream_get_le16(&buf);
  72     if (avcodec_check_dimensions(avctx, w, h) < 0)
  73         return -1;
  74     x = bytestream_get_le16(&buf);
  75     y = bytestream_get_le16(&buf);
  76     // skip bottom right position, it gives no new information
  77     bytestream_get_le16(&buf);
  78     bytestream_get_le16(&buf);
  79     rlelen = bytestream_get_le16(&buf);
  80
  81     // allocate sub and set values
  82     if (!sub->rects) {
  83         sub->rects = av_mallocz(sizeof(AVSubtitleRect));
  84         sub->num_rects = 1;
  85     }
  86     av_freep(&sub->rects[0].bitmap);
  87     sub->rects[0].x = x; sub->rects[0].y = y;
  88     sub->rects[0].w = w; sub->rects[0].h = h;
  89     sub->rects[0].linesize = w;
  90     sub->rects[0].bitmap = av_malloc(w * h);
  91     sub->rects[0].nb_colors = 4;
  92     sub->rects[0].rgba_palette = av_malloc(sub->rects[0].nb_colors * 4);
  93
  94     // read palette
  95     for (i = 0; i < sub->rects[0].nb_colors; i++)
  96         sub->rects[0].rgba_palette[i] = bytestream_get_be24(&buf);
  97     // make all except background (first entry) non-transparent
  98     for (i = 1; i < sub->rects[0].nb_colors; i++)
  99         sub->rects[0].rgba_palette[i] |= 0xff000000;
 100
 101     // process RLE-compressed data
 102     rlelen = FFMIN(rlelen, buf_end - buf);
 103     init_get_bits(&gb, buf, rlelen * 8);
 104     bitmap = sub->rects[0].bitmap;
 105     for (y = 0; y < h; y++) {
 106         // interlaced: do odd lines
 107         if (y == (h + 1) / 2) bitmap = sub->rects[0].bitmap + w;
 108         for (x = 0; x < w; ) {
 109             int log2 = ff_log2_tab[show_bits(&gb, 8)];
 110             int run = get_bits(&gb, 14 - 4 * (log2 >> 1));
 111             int color = get_bits(&gb, 2);
 112             run = FFMIN(run, w - x);
 113             // run length 0 means till end of row
 114             if (!run) run = w - x;
 115             memset(bitmap, color, run);
 116             bitmap += run;
 117             x += run;
 118         }
 119         // interlaced, skip every second line
 120         bitmap += w;
 121         align_get_bits(&gb);
 122     }
 123     *data_size = 1;
 124     return buf_size;
 125 }
 126
 127 AVCodec xsub_decoder = {
 128     "xsub",
 129     CODEC_TYPE_SUBTITLE,
 130     CODEC_ID_XSUB,
 131     0,
 132     decode_init,
 133     NULL,
 134     NULL,
 135     decode_frame,
 136     .long_name = "XSUB",
 137 };